M. P. A. Favre's Electrolytic Investigations. 297 



posed by even the most energetic voltaic current capable of di- 

 7 , ecthj effecting the chemical separation of compounds far more 

 stable than it. Hence it is not the nascent hydrogen which 

 liberates the metal of the salts held in solution in the voltameter. 



Assuming that water could be decomposed by the voltaic cur- 

 rent, the secondary phenomenon of the reduction of salts would 

 be inadmissible — in the case of sulphate of zinc, for instance. In 

 fact, in the voltameter, nascent hydrogen cannot be substituted 

 for the zinc of sulphate of zinc ; while in the battery it is the 

 contrary phenomenon, of the substitution of zinc for the hydrogen 

 of the sulphate of hydrogen, which produces the current. 



Assuming also that, contrary to Faraday's law, the voltaic 

 movement could effect the double electrolysis of water into its 

 simple elements (acid and metallic oxide), the reduction of me- 

 tallic oxide by nascent hydrogen ( which as an extreme case 

 might be conceived to extend to oxide of copper) is inadmissible 

 in the case of oxide of zinc, and with still greater reason in 

 that of oxide of potassium. 



Water constitutes, then, the very mobile medium in which 

 the electrolyte can freely move and adjust itself, in conformity 

 with the explanation which Grotthiiss has given of the transport 

 to the two poles. This water can only be decomposed (in an in- 

 direct manner) by the battery in case its tension is great enough 

 to allow the current to traverse the space separating the elec- 

 trodes, and to raise the temperature sufficiently for a repetition 

 of Grove's experiment of the decomposition of water by incan- 

 descent platinum. 



It would seem that the chemical action produced in the bat- 

 tery, and which puts in play the constituent molecules of the 

 saline compounds, produces in the circuit a very simple motion, 

 which can only be transmitted to the constituent molecules of 

 compounds of the same order. Thus the chemical decomposi- 

 tion of these compounds may be produced when the number of 

 couples is so multiplied that the voltaic motion developed acquires 

 a sufficient amplitude to transport the constituent molecules out- 

 side their sphere of activity. 



Thus nitric acid, which cannot be directly deoxygenized in the 

 voltaic circuit (from which it need not, however, borrow much 

 heat), is directly decomposed, borrowing a much more consider- 

 able quantity of heat ; but it is as a saline compound — that is, 

 with the separation of the metalloid NO 6 and of the metal H. 



I have showed* that a pressure of about 85 atmospheres does 

 not oppose the decomposing action of the current. 



* " Researches on the Influence of Pressure on some Physical and Che- 

 mical Phenomena," Comptes Rendus de VAcademie des Sciences, vol. li. 

 pp. 827 & 1027. 



